Structure of the Λ(1405) baryon resonance from its large Nc behavior

We study the behavior with the number of colors (N-c) of the two poles associated to the Lambda(1405) resonance obtained dynamically within the chiral unitary approach. The leading order chiral mesonbaryon interaction manifests a nontrivial N-c dependence for SU(3) baryons, which gives a finite attractive interaction in some channels in the large N-c limit. As a consequence, the SU(3) singlet ((K) over barN) component of the Lambda(1405) survives in the large N-c limit as a bound state, while the other components dissolve into the continuum. The N-c dependence of the decay widths shows different behavior from the general counting rule for a qqq state, indicating the dynamical origin of the two poles for the Lambda(1405) resonance.